Abstract

This report encompasses survey results providing clinically important, unpublished findings of the medical conditions of captive ursids in zoos and aquaria throughout North America. Surveys were distributed to facilitate the creation of a husbandry manual for captive ursids. Records from 50 institutions current through Fall 1999–Spring 2000 were used to compile this data. Selected findings reported here have been limited to three major body systems. Medical issues of polar (Ursus maritimus), brown (Ursus arctos), North American black (Ursus americanus), Asiatic black (Ursus thibetanus), sloth (Melursus ursinus), sun (Helarctos malayanus), and spectacled bears (Tremarctos ornatus) are discussed within the digestive, ocular, and integumentary systems. Chronic keratitis as well as gastric dilation and volvulus were found to be predominant lesions in sun bears. Neoplasia encompassed forty-percent of all digestive cases identified (including gastrointestinal, hepatic, and biliary tissues). Eleven percent of all bears surveyed had some type of skin disease. Further evaluation of captive bears is ongoing through the cooperation of the AZA Bear Taxonomic Group member institutions.

Introduction

The medical records and historical data for 512 bears, held within 50 zoos and aquaria within the United States, Canada, and Mexico, were examined and used to compile this data. Among these bears, 103 or 20.1% were North American black bears, 95 or 18.6% were polar bears, 91 or 17.7% were brown bears, 68 or 13.3% were sun bears, 66 or 12.9% were spectacled bears, 46 or 9% were sloth bears and 43 or 8.4% were Asiatic black bears. Although giant panda (Ailuropoda melanoleuca) were included in the survey, no records or results were obtained for this species. The following data encompasses information obtained from this survey.

Materials and Methods

Surveys were distributed to 157 zoos and aquaria in the Unites States, Canada, and Mexico, which have, or historically had, bears in their collection. Surveys were distributed in August 1999 and encompassed vaccination records and policies, anesthetics used, enrichment, conditioning, parasitism, and occurrence and treatment of disease based on an organ system breakdown. Institutions were requested to complete the survey and/or return complete medical records for review. Both current medical records and historical (up to 10 years previous) were obtained from fifty institutions. Records were received in various formats ranging from hand-written to complete MedARKS files. Data was obtained via investigation of records and completed surveys. Interpretation of records proved challenging and dependence on the empirical diagnosis listed within was necessary. Institutions are identified in a generic way in order to maintain confidentiality.

Results

Seventeen cases of ocular disease were found within the records of 512 captive bears. Nine of these 17 (53%) cases of eye disease were found in sun bears with seven of 9 cases reported as a chronic keratitis, one as a corneal neoplasia (squamous cell carcinoma of the left eye, keratitis of the right eye, and melanoma of the eyelid), and one as a probable lacrimal duct aplasia. Chronic keratitis was not reported in any species other than sun bears. Four of 17 (23.5%) total cases were listed as conjunctivitis with three (75%) found in spectacled bears and one case of chronic conjunctivitis was found in a North American black bear. Of the four remaining cases the distribution was as follows: two cases of corneal trauma in Asiatic black bears, one case of chronic contact irritation in a polar bear, and one case of diabetic cataracts in a brown bear (Table 1).

Table 1. Summary of ocular disease survey data. Data represent number of individual cases per species and disease as well as the coordinating percentage of total cases.

Survey results for digestive system conditions was divided into gastrointestinal and hepatobiliary conditions. A total of 61 bears were found to have exhibited disease of the digestive system, 45 of which were gastrointestinal cases and 16 were either hepatic or biliary cases.

Gastrointestinal neoplasia included:

• Pancreatic adenocarcinoma in a sloth bear
• Pancreatic adenoma in an Asiatic black bear
• Squamous cell carcinoma in a spectacled bear and a north American black bear
• Malignant melanoma of the hard palate in a brown bear
• An unspecified small intestinal neoplasia in a sun bear
• Intestinal adenocarcinoma in a sun bear and a brown bear
• Disseminated abdominal adenocarcinoma in a brown bear
• Intestinal lymphosarcoma in a brown bear (possibly causing mesenteric torsion)
• Lymphosarcoma (affecting hepatic and renal tissues) in an Asiatic black bear
• Lymphocytic lymphoma in a brown bear
• Papillary cystadenocarcinoma in a sun bear

Gastrointestinal medical conditions included:

• Inflammatory bowel disease (IBD) in two polar bears and one sun bear
• Gastric dilatation and volvulus (GDV) in four sun bears and a polar bear
• Enteritis/colitis, foreign body ingestion, dietary indiscretion, hematochezia of unknown origin in three sloth bears
• Constipation, strangulated and ruptured intestine, gastric fungal granuloma in a North American black bear
• Mesenteric torsion possibly secondary to lymphosarcoma, megaesophagus in a polar bear
• formula stasis, and diabetes (type unspecified) in a brown bear (Tables 2 and 3)

Table 2. Summary of gastrointestinal disease survey data. Data represent number of individual cases per species and disease as well as the coordinating percentage of total cases.

Table 3. Summary of hepatic/biliary disease survey data. Data represent number of individual cases per species and disease as well as the coordinating percentage of total cases.

The following hepatic cases were described in this survey:

• Hepatocellular carcinoma in three brown bears
• Liver adenocarcinoma in a polar bear
• An unspecified tumor in a polar bear
• Benign hepatoma in a polar bear
• Biliary carcinoma in a brown bear
• Cholangiosarcoma in a spectacled bear
• Cholangiocellular carcinoma in two sloth bears, a polar bear, and a brown bear

Non-neoplastic disease of the hepatobiliary tract included one case of hepatitis in a polar bear which was consistent with a viral etiology although not confirmed. Vacuolar hepatopathy in a sun bear, chronic cholangitis due to intestinal neoplasia in a sun bear, and cholestasis due to a metastatic mass in a spectacled bear were also found in the survey results (Table 3).

Diseases of the integumentary system appears common in captive species with 11% of bears reviewed in this report have been documented skin disease.

Various causative factors have been reported including:

• Endocrine disease (confirmed hypothyroidism and suspected endocrine/estrogen related disease)
• Mites (Demodex spp.)
• Fly bites
• Fire ants
• Brown recluse spider bites
• Ringworm
• Fungal and bacterial infection (Dermatophilus and Staphylococcus are documented)
• Self-mutilation
• Seasonal changes

Among all documented cases of alopecia, dermatitis, pruritis, or a combination of these, 29% were undiagnosed (Table 4).

Table 4. Summary of integumentary disease survey data. Data represent number of individual cases per species and disease as well as the coordinating percentage of total cases.

Discussion

Ocular disease, particularly chronic keratitis, was found to predominate in sun bears. The cause of this predisposition to chronic keratitis is unknown but it is speculated that a genetic predisposition may be to present or that chronic sun exposure in this rainforest species may influence this development. One case, as examined by a veterinary ophthalmologist, was described as solar induced corneal dysplasia and/or endothelial dysplasia of unknown cause. The syndrome was described in this case as ulcerative with progression to permanent white scarring with eventual vision impairment. Additionally, one case of ocular nodular fasciitis, similar to canine fibrous histiocytoma, has been reported and successfully removed in an Asiatic black bear.⁶

Neoplasia at 28% of the cases was by far the predominant finding in the gastrointestinal system. Gastrointestinal volvulus has also been described as a cause of death in a free ranging polar bear with gastric dilatation and volulus¹ and a captive black bear with small intestinal volvulus.¹¹ In addition, biliary carcinoma in two sun bears, pancreatic adenoma in a brown bear, pancreatic necrosis in two brown bears, one North American black bear, and one sun bear are reported and previously published from a single institution.² Obstruction due to trichobezoars (hair balls) has also been reported as a cause of death in a captive sloth bear.⁸ It is interesting to note that fungal enteritis and pneumonia has also recently been seen in captive sun bears imported from the wild. Lesions in this case resembled neoplastic foci; however, they were fungal in origin. Future differential diagnoses in sun bears should take this finding into account. Among diseases noted in the hepatic system, 76% were neoplastic. The survey cases were divided equally between the hepatic parenchyma and the biliary system.

Integumentary diseases were widespread and commonly undiagnosed despite thorough workups. In addition to the case noted through this research, dermatophilosis has also been reported in the literature in two of thirteen captive polar bears at a single institution.⁷ Cases of mites, including Ursicoptes americanus and Sarcoptes scabiei in North American black bears have also been reported in the literature.^10,12 Both reports suggest immunocompromise as an underlying factor in the clinical mange exhibited. One report has described the use of naltrexone for the treatment of psychogenic dermatoses without success in a polar bear.⁵ Hypothyroidism as an endocrine related cause of skin disease should be considered as reported in the postmortem findings in a brown bear.^3,9

Conclusions

The selected findings of this report describes the disease prevalence of the ophthalmic, digestive, and integumentary systems within captive bear populations in the United States, Canada, and Mexico. Results represent diseases seen at the fifty institutions participating in the survey. However, as some species are more commonly seen in zoos than others, interpretation of results must be relative to the proportions surveyed. Results suggest a predisposition of sun bears to the development of chronic keratitis. More research is needed to elucidate the cause of this condition and to enact preventive measures if possible. Additionally, there appears to be a predominance of GDV in sun bears with only one other case seen in a polar bear. Although no trends were seen on a species basis, enteritis, colitis, and inflammatory bowel disease were common findings. Most certainly, neoplasia was the most common finding in the digestive system. However, no dominant tumor type was elucidated. Of all neoplasias documented, the most common types of tumors were hepatocellular carcinoma and cholangiocellular carcinoma. The results of this survey help facilitate the consultation of the Bear TAG, Veterinary Advisory Group on captive bear disease within both AZA and non-AZA institutions to establish disease trends, share successful treatment modalities and identify areas for further research and investigations.

Acknowledgments

This work was supported by a grant from the Geraldine R. Dodge Foundation. Appreciation is extended to Woodland Park Zoo for administrative assistance and support and to all the institutions taking part in the survey.

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